In a modern power system, with the increasing scale of interconnected power grid, the capacity of the remote power transmission is increasing, the low frequency oscillation of the power grid in China occurs frequently. How to perform online real-time measurement and identification on low frequency oscillation rapidly and accurately with a small disturbance analysis method is a critical issue to be addressed in the large scale interconnected power grid. A traditional and classical method for analyzing low frequency oscillation is a method for analyzing eigenvalues with a small disturbance. For an anticipated operation mode of a system, information including low frequency oscillation sub-groups, oscillation relationship, and correlation factors, etc., is derived from an analysis of eigenvalues and eigenvectors of a status equation of operating points. The method for analyzing stability with small disturbance generally makes an offline analysis. However, the oscillation mode of the power system typically varies with a varying operation condition thereof, so accurate online calculation can not be guaranteed from an offline derived result.
A Wide Area Measurement System (WAMS) is a means to monitor the dynamic process of a power system. It can measure variables which are closely related to the transient electromechanical process of a generator rapidly, such as the internal potential, power angle, angular velocity, bus-bar voltage, etc., of the generator, and transmits the information to a centralized station in time to provide the possibility of performing an online analysis and control for the low frequency oscillation. Currently, however, the WAMS in operation and documents concerning WAMS based detection of low frequency oscillation are only limited to a dynamic monitoring function. That is, dynamic curves of a power grid for the voltage relative phase angle, frequency and power are monitored continuously, to real-time calculate and analyze the spectrum of the dynamic curves. Upon detection of presence of a relatively-strong weak damping oscillation component in the range of 0.2 to 2.5 Hz, warning information is transmitted to a dispatching operator, an abnormal zone is marked on a regional map of the power grid, and a data platform is triggered to record current real-time data at a high speed. However, it is impossible to install Phasor Measurement Units (PMUs) at all the nodes of a power system in view of the cost. Typically, an oscillation characteristic of power at an outlet port of a line or station is derived with the WAMS monitoring function, and therefore it is impossible to determine which specific ones of generators give rise to oscillation. That is, no control measure can be taken against oscillation due to absence of further analytical information of a low frequency oscillation mechanism.